1. Field of the Invention
The present invention relates to an anti-panic mechanism of a vehicle door latch device.
2. Description of the Related Art
In the conventional prevailing vehicle door latch devices, unlocking operations by an inside lock button, a remote control transmitter and the like are not normally completed if the outside open handle of a door is in the state of being manipulated by an opening operation, nor is it possible to open the door. Such a state is referred to as a panic state in the industry. When plunged into the panic state, the outside open handle is restored to a non-operation state and, then, the unlocking operation is performed again by the central door lock system and the like and, after that, the opening operation of the door handle is performed again, so that the door is opened. That is, two unlocking operations and two door opening operations are required until the door is opened. Thus, in the present invention, a state, in which two unlocking operations and two door opening operations are required, is defined as a full panic state.
A door latch device comprising an anti-panic mechanism to reduce a complication of operations due to the occurrence of the full panic is also known (Japanese Utility Model Application Laid-Open No. 58-101949 and Japanese Patent Application Laid-Open No. 11-324451). The prior antic-panic mechanism is a mechanism aiming to eliminate the second unlocking operation. In the prior art device, in the case where the first unlocking operation is not normally completed by the first opening operation of the door handle, a shifting to the unlocked state is completed when the door handle is restored to the non-operation state. Hence, when the second opening operation of the door handle is subsequently performed, it is possible to open the door even if the second unlocking operation is not performed. Thus, the state, in which single unlocking operation and two opening operation are required, is defined as a semi-panic state as against the full panic state.
The above described two types of panic states occur when the shifting to the locked state from the unlocked state of the door latch device falls behind the opening operation by the outside door handle.
For example, even after the unlocking operation was performed by the remote control transmitter, the central door lock system, the smart entry mechanism as described in Japanese Patent Application Laid-Open No. 11-141211, the panic state occurs when the opening operation is performed by the outside door handle before the shifting to the unlocked state from the locked state of the door latch device is completed.
Here, the completion of the shifting to the unlocked state from the locked state can be regarded as corresponding to the timing in which a lock lever of the door latch device crosses over a dead point of an over center spring arranged between the unlocked position and the locked position. Therefore, even after the unlocking operation was performed by the switch of the central door lock and the like, the panic state occurs when the outside door handle is manipulated before the lock lever crosses over the dead point by the motor power. Since such a timing of the panic state occurrence is common to the conventional door latch devices regardless of the presence or absence of the anti-panic mechanism, the conventional anti-panic mechanism has been such that it is not possible to reduce the frequency of occurrences even if it can change the types of the panic states from the full panic state to the semi panic state.
However, it is possible to obtain a substantial unlocked state by the motor power at an early stage before the lock lever crosses over the dead point of the over center spring so as to make the door opening operation effective, and the frequency of occurrences of the panic state can be reduced.